Hello,
There are actually quite a few areas within an hour drive of newcastle to shoot Dogs. Yes, the plaque did come through and "naturally" eliminate alot of them. Most of the area is private land. With some driving and a good map, you can find some towns on public land that has public access. The experiences you had with long shots are very common here. These dogs have been shot at for so many years that they've become smart. I would say that the majority of the dog towns are "educated" and you will have to shoot at least 200 yds most of the time, with 300 to 500 yd shots being most common. Of course, in most of this area a person could shoot out as far as they wish.
You may be able to find some uneducated towns, but most are "long range"
Most of the landowners allow prarie dog shooting, some might charge a small trespass fee however. Nearly all of them (charge or not) have people coming in on a fairly regular basis during the spring/summer months. This makes for some long range shooting.